A sound engineer needs one of the expertise necessary for good sound: loudness

Hearing is people's subjective response to sound. We know that any complex sound can be described in terms of three physical quantities of sound: amplitude (sound intensity or pressure), frequency, and phase. But for...

As far as the human ear is concerned, sound is described by three other quantities, namely loudness, pitch and timbre, which are commonly referred to as the "three elements of sound". In addition, the human ear can distinguish the dimensions of a sound

The distance to and from the human ear.

First, loudness

The loudness of a sound is related to the amplitude of the sound wave (sound pressure), and for a signal of the same frequency, the greater the sound pressure, the greater the loudness. But the loudness perception (sensitivity) of the human ear to sounds of different frequencies is

Different, that is, for different frequencies and the same sound pressure of the sound, will feel different loudness. Sounds in the 3 to 4 KHZ frequency range are easily perceived (higher sensitivity), while lower or

Sounds in the higher frequency range are not easily perceived. The curve describing the relationship between sound pressure level and frequency under the condition of equal loudness is called equal loudness curve.

The horizontal coordinate in the figure represents the pure tone signal of different frequencies, the unit is Hertz (Hertz); The ordinate represents the amplitude of the corresponding sound wave (sound pressure level); The curve in the figure is the equal loudness curve, and the unit is square loudness

(PHONO). Different units on the same loudness curve are decibel (dB) frequencies and pure tone signals with different sound pressure levels, giving people the same loudness feeling. For example: 50 dB /100 Hz pure

The sound is equal to the pure sound of 40 dB /1 KHZ, because both lie on the same equal sound curve. In other words, if you want to make a 100 Hz bass sound as loud as a 40 dB /1 KHZ alto, you have to make

A 100-hertz signal is 10 decibels larger than 1 KHZ. From the figure, we can draw the following simple conclusions:

1, the sensitivity of the human ear to different frequencies is not the same. Specifically, the sensitivity of 3 to 4 KHZ sound is high, and the general trend is as the frequency increases and decreases to both ends of 3 to 4 KHZ

It's reduced sensitivity.

2, the sensitivity of the human ear to different frequencies of sound is also related to the size of the sound pressure, with the reduction of sound pressure, the sensitivity of the human ear to low frequency and high frequency should be reduced, especially for low frequency sound.

This is why when we turn the volume down (i.e. in the case of low pressure levels), even though there is already more bass in the program, it still sounds low, once the volume is turned up

(Sound pressure level is roughly above 80 decibels), you will feel the truth that the bass is richer.

The equal-loudness curve shows that if the sound is replayed at a pressure level lower than the original sound (recorded), the bass and treble need to be raised by an equalizer to ensure the original timbre balance. For example a band

If the low frequency sound and high frequency sound are recorded at about 100 decibels, because the equal loudness curve at this time is almost flat, so the bass and the treble sound have the same loudness. if

Playback at a lower sound pressure level, such as 50 decibels, when the 50 Hz sound can just be heard, and 1 KHZ sound has 50 square sound, other different frequencies of sound have different loudness

Therefore, it sounds like the low frequency sound and high frequency sound are lost, that is, the original timbre has changed. At this point, you want to make the sound of 50 Hertz sound roughly the same as the sound of 1 KHZ

With the same loudness, it must be raised by about 20 decibels. It can be seen that the equal loudness curve is one of the important bases for us to use the equalizer.